EFFECT OF SMALL BULK SULFUR CONTENT AND ANNEALING TEMPERATURE ON THE INTERGRANULAR FRACTURING SUSCEPTIBILITY OF METALLIC NICKEL
Abstract
In this paper, we investigate the influence of temperature on the nickel grain boundary equilibrium segregation of sulfur and the resulting intergranular fracturing susceptibility. Auger electron spectroscopy has been used to study equilibrium segregation of sulfur to the grain boundaries of a metallic nickel, with a mass bulk content of 3.6ppm in sulfur. Samples were first annealed at adequate temperatures for sufficiently large equilibrium time, and then quenched in water at room temperature. The analysis carried out shows a significant increase of sulfur concentration in the grain boundary with decreasing temperature. However, the sulfur content in the grain boundary shows a drastic shrink at 700∘C. This can be interpreted by the formation of an aggregate sulfide compound in the area of the grain boundaries. At 650∘C, in situ brittle fracture becomes unworkable and only intragranular fractures are observed. Using the results obtained through the investigation of the grain boundaries by Auger spectroscopy, the standard segregation energy is estimated as ΔG0=−(100÷76) kJ∕mol.
